The proposed research will involve measurement of Ca segregation and changes in flexural strength of two orthopedic-grade aluminas, Feldmuhle "Biolux" and McDanel "998", following exposure to conditions similar to the human body. Effects of aging in demineralized H2O and Ringer's solution at 37 degrees and 70 degrees Centigrade for durations of 3 to 52 weeks will be determined. Other samples, subcutaneously implanted in rats, will be removed for analyses after aging for 6 to 52 weeks in vivo. In addition, time-to-failure (static fatigue) measurements will be initiated on stressed samples (loaded to 50, 70, and 90% of dry flexural strength) immersed in demineralized H2O or Ringer's solution at both 37 degrees and 70 degrees Centigrade. Calcium concentration profiles will be performed by Auger electron spectroscopy. Three point bend tests will be utilized for both flexural strength and time-to-failure measurements. The proposed research will determine effects of Ca segregation on long-term service performance of orthopedic-grade aluminas.